Psyllids arrive early in PNW

By John O’Connell

Capital Press

Published:June 6, 2014 9:19AM

Last changed:June 9, 2014 10:48AM

Submitted by Joseph Munyaneza

Markings on potato chips from zebra chip darken when fried. Researchers say the tiny, winged insects that can spread zebra chip disease in potato fields have been detected in Idaho, Washington and Oregon earlier than ever before.

Potato psyllids, which can spread zebra chip disease in potato fields, have arrived in the Pacific Northwest early this season, experts say.

Researchers say the tiny, winged insects that can spread zebra chip disease in potato fields have been detected in Idaho, Washington and Oregon earlier than ever before.

Confirmed potato psyllids are being tested for their haplotype and the presence of the Liberibacter bacterium that causes zebra chip. Bands that darken when fried riddle the flesh of infected tubers.

“It’s probably two to three weeks earlier than we’ve ever detected (psyllids) previously,” said Tim Waters, a Washington State University Extension educator for Franklin and Benton counties. “It’s a little bit concerning because it’s an insect that will build in numbers throughout the year.”

Waters said WSU confirmed a single psyllid from potato leaf samples recently taken from a university research field in Pasco, Wash. He emphasized regional psyllid numbers appear to still be extremely small, and crop experts are becoming more accustomed to spotting the bugs.

The disease originated in Mexico in the early 1990s and was identified in Texas in 2000. It first surfaced in the Pacific Northwest in 2011. Zebra chip caused headaches for PNW growers, especially in Idaho, in 2012 and has forced farmers to implement costly preventative pesticide and field scouting programs, but the incidence of zebra chip was extremely low in 2013.

Joe Munyaneza, a research entomologist with the USDA’s Agricultural Research Service in Yakima, Wash., said he recently identified a psyllid from a crop consultant’s sample originating from a commercial potato field in Washington’s Columbia Basin.

Oregon State University Extension entomologist Silvia Rondon has also made a positive psyllid identification from a sticky trap taken from a commercial field in the Lower Columbia Basin in Oregon. Rondon said two psyllid nymphs were confirmed from Oregon experimental fields.

“We are seeing psyllids move into potatoes as we speak, and it seems to be early relative to other years,” Rondon said. “The important thing for (growers) is to keep a really close eye on psyllid movement right now and start trapping for them.”

University of Idaho Extension entomologist Erik Wenninger said the Gem State’s first psyllid was confirmed on a sticky card deployed to a Jerome County potato field on May 27 and retrieved June 3. He said six psyllids were also recently found from two bittersweet nightshade monitoring sites in Twin Falls County.

Wenninger said it’s unclear if the psyllids overwintered in the PNW, or why they’ve arrived early this year.

“It’s a little early to tell what kind of psyllid year we’re going to have, but it’s certainly worthy of note that we found psyllids earlier this year,” Wenninger said.

Wenninger said Idaho has reduced its psyllid monitoring program this year to include about 80 fields, compared with more than 100 last season. He has no new recommendations for growers regarding spraying. Zebra chip infection rates were too low last season to draw conclusions from insecticide trials.

This season, Wenninger said insecticide trials will utilize smaller plots inoculated with Liberibacter instead of relying on the disease to arrive naturally.